Camera provided with eyepiece

ABSTRACT

A camera includes a screen on which an image of an object is projected, a plurality of reflection surfaces for erecting the image on the screen, and an eyepiece system with positive refracting power for observing the image. In this case, the eyepiece system includes, in order from the object side, a first lens component with positive refracting power, a second lens component with positive refracting power, and a third lens component with negative refracting power. Spacings between the first lens component and the second lens component and between the second lens component and the third lens component are changed to thereby make a diopter adjustment, and the camera satisfies the following conditions: 
     0.15&lt;tan(S)&lt;0.35 
     2.00&lt;fb/Y&lt;4.00 
     −0.80&lt;f3/f&lt;−0.40 
     where S is an angle, at a diopter of 0 m −1 , made by the most off-axis chief ray passing through a point on the optical axis at a distance of 23 mm along the optical axis from the exit surface of the third lens component with the optical axis; fb is an air-equivalent length, at a diopter of 0 m −1 , from the screen to the entrance surface of the first lens component; Y is a diagonal length of the picture plane on the screen; f3 is the focal length of the third lens component; and f is the focal length, at a diopter of 0 m −1 , of the entire system from the screen to the exit surface of the eyepiece system.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a camera provided with an eyepiece, andin particular, to a camera having a picture plane of size as small asnearly half of a 135-format film or a silver halide 35-nm film.

[0003] 2. Description of Related Art

[0004] In a camera having a picture plane of small size, when aconventional eyepiece is used as it is, an observation image becomessmall and an photographer suffers from undue fatigue in using thecamera.

[0005] Thus, in order to enable a large image to be observed through afinder, it is necessary to reduce the focal length of the eyepiece andto increase a finder magnification.

[0006] Conventional examples in which the focal length of the eyepieceis reduced are disclosed in Japanese Patent Publication Nos. Sho57-60612 and Hei 7-107581 and Japanese Patent Kokai No. Hei 11-337847.

[0007] In order to render a finder easy to see, there is the need toensure a distance from the eyepiece to the pupil position of an observeras long as possible and to minimize vignetting. In this case also, itbecomes necessary to sufficiently increase a distance from anobservation plane to a first lens component of the eyepiece.

[0008] An eyepiece in which the distance from the observation plane tothe entrance surface of the first lens component thereof is longer thanthe focal length is set forth, for example, in Japanese Patent No.2726261 in addition to Publication No. Hei 7-107581 mentioned above.

SUMMARY OF THE INVENTION

[0009] The present invention provides a single-lens reflex camera whichcomprises a screen on which an image of an object is projected, aplurality of reflection surfaces for erecting the image on the screen,and an eyepiece system with positive refracting power for observing theimage. In this case, the eyepiece system includes, in order from theobject side, a first lens component with positive refracting power, asecond lens component with positive refracting power, and a third lenscomponent with negative refracting power so that spacings between thefirst lens component and the second lens component and between thesecond lens component and the third lens component are changed tothereby make a diopter adjustment, and the single-lens reflex camerasatisfies the following conditions:

0.15<tan(S)<0.35  (1)

2.00<fb/Y<4.00  (2)

−0.80<f3/f<−0.40  (3)

[0010] where S is an angle, at a diopter of 0 m⁻¹, made by the mostoff-axis chief ray passing through a point on the optical axis at adistance of 23 mm along the optical axis from the exit surface of thethird lens component with the optical axis; fb is an air-equivalentlength, at a diopter of 0 m⁻¹, from the screen to the entrance surfaceof the first lens component; Y is a diagonal length of the picture planeon the screen; f3 is the focal length of the third lens component; and fis the focal length, at a diopter of 0 m⁻¹, of the entire system fromthe screen to the exit surface of the eyepiece system.

[0011] Further, the present invention provides a camera which comprisesa screen on which an image of an object is projected, a plurality ofreflection surfaces for erecting the image on the screen, and aneyepiece system with positive refracting power for observing the image.In this case, the eyepiece system includes, in order from the objectside, a first lens component with positive refracting power, a secondlens component with positive refracting power, and a third lenscomponent with negative refracting power so that spacings between thefirst lens component and the second lens component and between thesecond lens component and the third lens component are changed tothereby make a diopter adjustment, and the camera satisfies Condition(1) and the following condition:

−0.65<f3/f<−0.45  (4)

[0012] Still further, the present invention provides a camera whichcomprises a screen on which an image of an object is projected, aplurality of reflection surfaces for erecting the image on the screen,and an eyepiece system with positive refracting power for observing theimage. In this case, the eyepiece system includes, in order from theobject side, a first lens component with positive refracting power, asecond lens component with positive refracting power, and a third lenscomponent with negative refracting power so that spacings between thefirst lens component and the second lens component and between thesecond lens component and the third lens component are changed tothereby make a diopter adjustment, and the camera satisfies Condition(1) and the following condition:

15 mm<Y<30 mm  (5)

[0013] The present invention provides a camera which comprises a screenon which an image of an object is projected, a plurality of reflectionsurfaces for erecting the image on the screen, and an eyepiece systemwith positive refracting power for observing the image. In this case,the eyepiece system includes, in order from the object side, a firstlens component with positive refracting power, a second lens componentwith positive refracting power, and a third lens component with negativerefracting power so that spacings between the first lens component andthe second lens component and between the second lens component and thethird lens component are changed to thereby make a diopter adjustment,and the camera satisfies Condition (1) and the following conditions:

2.70<fb/Y<3.20  (6)

−0.80<f3/f<−0.30  (7)

[0014] According to the present invention, preferably, each of the firstlens component, the second lens component, and the third lens componentis constructed with a single lens or a cemented lens.

[0015] According to the present invention, preferably, only the secondlens component is moved to thereby make a diopter adjustment.

[0016] The present invention provides a camera which comprises a screenon which an image of an object is projected, a plurality of reflectionsurfaces for erecting the image on the screen, and an eyepiece systemwith positive refracting power for observing the image. In this case,the eyepiece system includes, in order from the object side, a firstlens component with positive refracting power, a second lens componentwith positive refracting power, and a third lens component with negativerefracting power, and the camera satisfies the following conditions:

2.5<fb′/Y<4.0  (8)

−1.0<f3/f′<−0.2  (9)

0.4<f1/f′<0.95  (10)

[0017] where fb′ is an air-equivalent length, at a diopter of −0.5(m⁻¹), from the screen to the entrance surface of the first lenscomponent; f′ is the focal length of the entire system from the screento the exit surface of the eyepiece system at a diopter of −0.5 (m⁻¹);and f1 is the focal length of the first lens component.

[0018] The present invention provides a camera which comprises a screenon which an image of an object is projected, a plurality of reflectionsurfaces for erecting the image on the screen, and an eyepiece systemwith positive refracting power for observing the image. In this case,the eyepiece system includes, in order from the object side, a firstlens component with positive refracting power, a second lens componentwith positive refracting power comprised of a single meniscus lenselement with a convex surface directed toward the object side, and athird lens component with negative refracting power as a whole in whichthe refracting power of a pupil-side surface is stronger than that of anobject-side surface, and the camera satisfies Conditions (8), (9), and(10).

[0019] In the present invention, instead of the screen on which theimage of the object is projected, the camera may be provided with anelectronic viewfinder which includes a liquid crystal display elementhaving an image plane for displaying the image of the object.

[0020] Alternatively, in the present invention, instead of the screen onwhich the image of the object is projected, the camera may be providedwith a finder which includes an objective optical system forming theimage plane of the object.

[0021] In these cases, Y becomes Y′ (a diagonal length of a pictureplane on the image plane), fb becomes f′b (an air-equivalent length fromthe image plane to the entrance surface of the first lens component at adiopter of 0 (m⁻¹)), fb′ becomes f′b′ (an air-equivalent length from theimage plane to the entrance surface of the first lens component at adiopter of −0.5 (m⁻¹)), f becomes f″ (the focal length, at a diopter of0 (m⁻¹), of the entire system from the image plane to the exit surfaceof the eyepiece system), and f′ becomes f′″ (the focal length, at adiopter of −0.5 (m⁻¹), of the entire system from the image plane to theexit surface of the eyepiece system).

[0022] These and other features and advantages of the present inventionwill become apparent from the following detailed description of thepreferred embodiments when taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a view showing schematically a camera according to thepresent invention;

[0024]FIG. 2 is an explanatory view of the screen of the cameraaccording to the present invention;

[0025]FIG. 3 is an explanatory view of an angle defined by a conditionin the present invention;

[0026]FIG. 4 is a sectional view showing an optical arrangement,developed along the optical axis, at a diopter of 0 m⁻¹, in a firstembodiment of an eyepiece optical system used in the camera according tothe present invention;

[0027]FIGS. 5A, 5B, 5C, and 5D are diagrams showing aberrationcharacteristics at a diopter of +1 m⁻¹ in the first embodiment; FIGS.6A, 6B, 6C, and 6D are diagrams showing aberration characteristics at adiopter of 0 m⁻¹ in the first embodiment;

[0028]FIGS. 7A, 7B, 7C, and 7D are diagrams showing aberrationcharacteristics at a diopter of −3 m⁻¹ in the first embodiment;

[0029]FIG. 8 is a sectional view showing an optical arrangement,developed along the optical axis, at a diopter of 0 m⁻¹, in a secondembodiment of an eyepiece optical system used in the camera according tothe present invention;

[0030]FIGS. 9A, 9B, 9C, and 9D are diagrams showing aberrationcharacteristics at a diopter of +1 m⁻¹ in the second embodiment;

[0031]FIGS. 10A, 10B, 10C, and 10D are diagrams showing aberrationcharacteristics at a diopter of 0 m⁻¹ in the second embodiment;

[0032]FIGS. 11A, 11B, 11C, and 11D are diagrams showing aberrationcharacteristics at a diopter of −3 m⁻¹ in the second embodiment;

[0033]FIG. 12 is a sectional view showing an optical arrangement,developed along the optical axis, at a diopter of 0 m⁻¹, in a thirdembodiment of an eyepiece optical system used in the camera according tothe present invention;

[0034]

[0035]FIGS. 13A, 13B, 13C, and 13D are diagrams showing aberrationcharacteristics at a diopter of +1 m⁻¹ in the third embodiment; FIGS.14A, 14B, 14C, and 14D are diagrams showing aberration characteristicsat a diopter of 0 m⁻¹ in the third embodiment;

[0036]FIGS. 15A, 15B, 15C, and 15D are diagrams showing aberrationcharacteristics at a diopter of −3 m⁻¹ in the third embodiment;

[0037]FIG. 16 is a sectional view showing an optical arrangement,developed along the optical axis, at a diopter of −0.5 m⁻¹, in a fourthembodiment of an eyepiece optical system used in the camera according tothe present invention;

[0038]FIGS. 17A, 17B, 17C, and 17D are diagrams showing aberrationcharacteristics at a diopter of +1 m⁻¹ in the fourth embodiment;

[0039]FIGS. 18A, 18B, 18C, and 18D are diagrams showing aberrationcharacteristics at a diopter of −0.5 m⁻¹ in the fourth embodiment;

[0040]FIGS. 19A, 19B, 19C, and 19D are diagrams showing aberrationcharacteristics at a diopter of −3 m⁻¹ in the fourth embodiment;

[0041]FIG. 20 is a sectional view showing an optical arrangement,developed along the optical axis, at a diopter of −0.5 m⁻¹, in a fifthembodiment of an eyepiece optical system used in the camera according tothe present invention;

[0042]FIGS. 21A, 21B, 21C, and 21D are diagrams showing aberrationcharacteristics at a diopter of +1 m⁻¹ in the fifth embodiment;

[0043]FIGS. 22A, 22B, 22C, and 22D are diagrams showing aberrationcharacteristics at a diopter of −0.5 m⁻¹ in the fifth embodiment;

[0044]FIGS. 23A, 23B, 23C, and 23D are diagrams showing aberrationcharacteristics at a diopter of −3 m⁻¹ in the fifth embodiment;

[0045]

[0046]FIG. 24 is a sectional view showing an optical arrangement,developed along the optical axis, at a diopter of −0.5 m⁻¹, in a sixthembodiment of an eyepiece optical system used in the camera according tothe present invention;

[0047]FIGS. 25A, 25B, 25C, and 25D are diagrams showing aberrationcharacteristics at a diopter of +1 m⁻¹ in the sixth embodiment;

[0048]FIGS. 26A, 26B, 26C, and 26D are diagrams showing aberrationcharacteristics at a diopter of −0.5 m⁻¹ in the sixth embodiment;

[0049]FIGS. 27A, 27B, 27C, and 27D are diagrams showing aberrationcharacteristics at a diopter of −3 m⁻¹ in the sixth embodiment;

[0050]FIG. 28 is a sectional view showing an optical arrangement,developed along the optical axis, at a diopter of −0.5 m⁻¹, in a seventhembodiment of an eyepiece optical system used in the camera according tothe present invention;

[0051]FIGS. 29A, 29B, 29C, and 29D are diagrams showing aberrationcharacteristics at a diopter of +1 m⁻¹ in the seventh embodiment;

[0052]FIGS. 30A, 30B, 30C, and 30D are diagrams showing aberrationcharacteristics at a diopter of −0.5 m⁻¹ in the seventh embodiment;

[0053]FIGS. 31A, 31B, 31C, and 31D are diagrams showing aberrationcharacteristics at a diopter of −3 m⁻¹ in the seventh embodiment;

[0054]FIG. 32 is a sectional view showing an optical arrangement,developed along the optical axis, at a diopter of −0.5 m⁻¹, in an eighthembodiment of an eyepiece optical system used in the camera according tothe present invention;

[0055]FIGS. 33A, 33B, 33C, and 33D are diagrams showing aberrationcharacteristics at a diopter of +1 m⁻¹ in the eighth embodiment;

[0056]FIGS. 34A, 34B, 34C, and 34D are diagrams showing aberrationcharacteristics at a diopter of −0.5 m⁻¹ in the eighth embodiment; and

[0057]FIGS. 35A, 35B, 35C, and 35D are diagrams showing aberrationcharacteristics at a diopter of −3 m⁻¹ in the eighth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] Before undertaking the description of the embodiments, thefunction of the present invention will be explained.

[0059] In order to increase the magnification of a finder system, it isonly necessary to reduce the focal length of the eyepiece. On the otherhand, however, an optical path length must be ensured in order toconstruct an image erecting system.

[0060] Since the camera provided with the eyepiece to which the presentinvention is applied has a high magnification and a considerable opticalpath length, it becomes difficult to construct the eyepiece.Furthermore, the size of the picture plane is small and hence the angleof emergence of light from the pupil is also small.

[0061] Thus, in order to increase the angle of emergence and facilitatethe observation of an object through the finder, the present inventionis designed to satisfy Condition (1).

[0062] In Condition (1), it is assumed that the pupil position of theobserver is located at a distance of 23 mm along the optical axis fromthe exit surface of the third lens component, and the maximum angle ofemergence at this position is represented by S.

[0063] If the upper limit of Condition (1) is exceeded, it becomesdifficult to completely correct aberration with a small number oflenses. Below the lower limit of Condition (1), the picture plane is sosmall that it becomes hard to see the object through the finder.

[0064] In order to satisfy the condition of the angle of emergence inCondition (1) and secure the optical path length for providing aplurality of reflection surfaces erecting the image, it is necessary toconstruct an optical system in which a front focal length is basicallylonger than the focal length.

[0065] Thus, in the present invention, the eyepiece is designed toinclude, in order from the object side, a first lens component withpositive refracting power, a second lens component with positiverefracting power, and a third lens component with negative refractingpower, and an optical system in which a distance from the entrancesurface of the first lens component to the screen is longer than thefocal length is achieved. Whereby, layout flexibility of the reflectionsurfaces can be secured.

[0066] In addition to such a basic construction, when the presentinvention is designed to satisfy at least one of Conditions (2), (7),and (5), a finder system through which the object is more favorably seencan be constructed.

[0067] Condition (2) prescribes a favorable air-equivalent length fromthe screen to the entrance surface of the first lens component.

[0068] In general, an image erecting optical system, such as apentagonal roof prism or a pentagonal roof mirror, is placed in spacebetween the screen and the entrance surface of the first lens component.Hence, the optical path length sufficient to place such a prism ormirror without any problem in the space between the screen and theentrance surface of the first lens component becomes necessary.

[0069] Below the lower limit of Condition (2), reflection surfaces areliable to cause interference. In the finder, on the other hand, anindication member is often placed on the periphery of the picture plane,and the optical path length which is long accordingly is required. Assuch, beyond the upper limit of Condition (2), it becomes difficult tocompletely correct aberration with a small number of lenses.

[0070] Condition (7) determines the focal length of the third lenscomponent in order to hold the balance between correction for aberrationand the security of the optical path length.

[0071] Below the lower limit of Condition (7) to weaken the negativerefracting power, it becomes difficult to ensure the optical pathlength. Beyond the upper limit of Condition (7) to strengthen thenegative refracting power, it becomes difficult to completely correctaberration with a small number of lenses.

[0072] Condition (5) determines the diagonal length of the picture planesuitable for the construction of the eyepiece mentioned above. Below thelower limit of Condition (5), it becomes difficult to obtain a desiredfield angle with a small number of lenses. Beyond the upper limit ofcondition (5), even though the construction of the eyepiece mentionedabove is not used, a satisfactory field angle and correction foraberration can be obtained. However, since the size of the picture planeis increased, compactness of the entire camera is highly limited.

[0073] In the diopter adjustment, when spacings between the first lenscomponent and the second lens component and between the second lenscomponent and the third lens component are changed for the diopteradjustment, the fluctuation of aberration caused by the diopteradjustment can be suppressed.

[0074] In order to make the diopter adjustment, only the second lenscomponent may be moved. In this case, the lens components located beforeand behind the second lens component which is a moving lens unit arefixed and, for example, spacings between these lens components arehermetically sealed. Whereby, dust penetration into the finder can beprevented.

[0075] When the optical system is designed to move the second lenscomponent alone, the first lens component is fixed, and other members(for example, a part of a stroboscopic contact mechanism and a part of afield indicating mechanism) can be placed in space surrounding this lenscomponent. This is favorable for compactness.

[0076] In the lens arrangement of the eyepiece, when each of the first,second, and third lens components is constructed with a single lens or acemented lens, correction for aberration and the security of the opticalpath length are completely achieved with a small number of lenses.

[0077] Furthermore, when the first lens component is configured into abiconvex shape, the second lens component is configured into a meniscusshape with a convex surface directed toward the object side or abiconvex shape, and the third lens component is configured into a shapesuch that the absolute value of a radius of curvature of the pupil-sidesurface is smaller than that of the object-side surface, aberration canbe corrected and the construction length of the eyepiece can be reduced,which is favorable.

[0078] In order to favorably correct aberration, notably chromaticaberration, it is desirable that at least one of the first lenscomponent and the second lens component is constructed with a cementedlens. In particular, when manufacturing costs are taken into account, itis more desirable that the cemented lens is used for the second lenscomponent which is reduced in lens diameter. In this case, when each ofthe first and third lens components is constructed with a single lens,the manufacturing costs can be further reduced.

[0079] When the second lens component is designed so that its interfacehas negative refracting power, the exit surface of the second lenscomponent need not necessarily have negative refracting power.

[0080] Subsequently, reference is made to favorable numerical limitswith respect to Conditions (1), (2), (7), and (5).

[0081] In Condition (1), it is more desirable that the lower limit isset to 0.20 or 0.22. It is more desirable that the upper limit is 0.3 or0.25.

[0082] In Condition (2), it is more desirable that the lower limit is2.70 or 2.95. It is more desirable that the upper limit is 3.0 or 3.20.

[0083] For example, it is more desirable to satisfy Condition (6).

[0084] In Condition (7), it is more desirable that the lower limit is−0.75 or −0.65. It is more desirable that the upper limit is −0.40,−0.45, or −0.50.

[0085] For example, it is more desirable to satisfy any one ofConditions (3) and (4) and the following condition:

−0.65<f3/f<−0.50  (11)

[0086] In Condition (5), it is more desirable that the lower limit isset to 17 mm or 20 mm. It is more desirable that the upper limit is 26mm. For example, it is more desirable to satisfy the followingcondition:

20 mm<Y<26 mm  (12)

[0087] When the eyepiece is constructed to have, in order from theobject side, the first lens component with positive refracting power,the second lens component with positive refracting power, and the thirdlens component with negative refracting power, the position of theprincipal point of the eyepiece system can be shifted to the object sideby the arrangement made in order of positive, positive, and negativerefracting powers, and the distance from the screen to the entrancesurface of the first lens component of the eyepiece system can beensured as a sufficient length.

[0088] When the second lens component is constructed with a meniscuslens element having a convex surface directed toward the object side,the position of the principal point of the eyepiece system can befurther shifted to the object side. This is more advantageous toensuring the distance from the screen to the entrance surface of thefirst lens component of the eyepiece system as a sufficient length.

[0089] According to the present invention, the height of an off-axischief ray passing through the object-side surface of the third lenscomponent is above that of the ray passing through the pupil-sidesurface thereof. Consequently, when the third lens component isconstructed with a lens component having negative refracting power as awhole in which the refracting power of the pupil-side surface isstronger than that of the object-side surface, the whole amount ofproduction of aberration can be minimized.

[0090] Subsequently, conditions will be described.

[0091] In the camera of the present invention, the image erectingoptical system, such as a pentagonal roof prism or a pentagonal roofmirror, is placed in space between the screen and the entrance surfaceof the first lens component of the eyepiece system. Hence, spacesufficient to place such a member without any problem becomes necessary.

[0092] It is thus favorable that the distance from the screen to theentrance surface of the first lens component of the eyepiece systemsatisfies Condition (8).

[0093] Below the lower limit of Condition (8), the space between thescreen and the entrance surface of the first lens component of theeyepiece system becomes insufficient and the image erecting opticalsystem ceases to be constructed. Beyond the upper limit of Condition(8), aberration cannot be completely corrected.

[0094] It is more desirable that the lower limit of Condition (8) is setto 2.8 or 3.0 and the upper limit of Condition (8) is 3.75 or 3.5.

[0095] For example, it is more desirable to satisfy one of the followingconditions:

2.8<fb′/Y<4.0  (8-1)

3.0<fb′/Y<3.75  (8-2)

[0096] As mentioned above, individual lens components are arranged tohave positive, positive, and negative refracting powers, and thenegative refracting power of the third lens component is strengthened sothat the position of the front principal point is shifted to the objectside of the eyepiece system. In this way, the distance from the screento the entrance surface of the first lens component of the eyepiecesystem is ensured as a sufficient length without increasing the focallength.

[0097] In this case, it is favorable to satisfy Condition (9).

[0098] Below the lower limit of Condition (9) to weaken the negativerefracting power of the third lens component, the effect that theposition of the front principal point is shifted to the object side ofthe eyepiece system is lessened, and the distance from the screen to theentrance surface of the first lens component of the eyepiece systemcannot be ensured as a sufficient length.

[0099] Beyond the upper limit of Condition (9) to strengthen thenegative refracting power of the third lens component, aberration cannotbe completely corrected.

[0100] It is more desirable that the lower limit of Condition (9) is setto −0.8 or −0.53 and the upper limit is −0.25 or −0.3.

[0101] For example, it is more desirable to satisfy one of the followingconditions:

−0.8<f3/f′<−0.2  (9-1)

−0.53<f3/f′<−0.25  (9-2)

[0102] In order to impart proper reflecting power to the first lenscomponent, it is favorable to satisfy Condition (10).

[0103] Below the lower limit of Condition (10) to strengthen thepositive refracting power of the first lens component, it becomesdifficult to completely correct aberration. Beyond the upper limit ofCondition (10) to weaken the positive refracting power of the first lenscomponent, the ray on the object side of the first lens componentbecomes high, and thus vignetting is caused by a prism interposedbetween the screen and the eyepiece system so that an eye relief cannotbe lengthened.

[0104] It is more desirable that the lower limit of Condition (10) isset to 0.45 or 0.5 and the upper limit is 0.87 or 0.85.

[0105] For example, it is more desirable to satisfy one of the followingconditions:

0.45<f1/f′<0.87  (10-1)

0.5<f1/f′<0.85  (10-2)

[0106] According to the present invention, the eyepiece system isdesigned so that the focal length is reduced and at the same time, thenegative refracting power is strengthened to shift the position of thefront principal point to the object side of the eyepiece system. Thus,any of individual lens components having positive and negativerefracting powers naturally becomes strong in power. Consequently, itbecomes difficult to correct axial chromatic aberration caused bymaintaining the balance of the refracting power between the lenscomponents with positive refracting powers and the lens component withnegative refracting power.

[0107] In order to set the distribution of refracting powers amongindividual lens components so that proper balance is acquired and tocorrect axial chromatic aberration more effectively, it is favorablethat the first lens component or the third lens component is constructedwith a cemented lens and the production of chromatic aberrations inindividual lens components is kept to a minimum.

[0108] It is desirable that, as described later, in view of the movementof the lens component for diopter adjustment, the second lens componentis constructed with a single positive meniscus lens to lessen the loadof a lens driving system.

[0109] When a high eyepoint is realized by the distribution of therefracting powers like the eyepiece of the present invention, the heightof the off-axis chief ray passing through the first lens component isliable to increase. Thus, since the difference of the height of theoff-axis chief ray between the first lens component with positiverefracting power and the third lens component with negative refractingpower becomes marked, both lens components are considerably different inthe amount of production of chromatic aberration of magnification and itis difficult to correct this aberration. As a result, chromaticaberration of magnification produced in the first lens componentremains. In order to keep the amount of this chromatic aberration ofmagnification to a minimum, it is effective for the first lens componentto use a low dispersion glass material. Specifically, it is goodpractice to use the glass material with an Abbe's number of not lessthan 80 for the first lens component, preferably not less than 80 normore than 100, or not less than 81 nor more than 95.

[0110] The size of the picture plane of the camera according to thepresent invention is nearly half of that of a silver halide film.

[0111] It is thus desirable that the eyepiece of the present inventionsatisfies the following condition:

16.0<Y<28.0  (13)

[0112] Below the lower limit of Condition (13) to reduce the size of thepicture plane, the magnification of the finder must be further increasedand a more complicated optical system is required.

[0113] Beyond the upper limit of Condition (13) to increase the size ofthe picture plane, the entire camera becomes bulky, which isunfavorable.

[0114] It is more desirable that the lower limit of Condition (13) isset to 18.0 or 20.0 and the upper limit is 27.0 or 26.0.

[0115] For example, it is more desirable to satisfy one of the followingconditions:

18.0<Y<27.0  (13-1)

20.0<Y<26.0  (13-2)

[0116] In order to make the diopter adjustment, it is desirable to movethe second lens component alone. By doing so, when spacings before andbehind the moving lens unit are hermetically sealed by the fixed lensunits, dust penetration into the finder can be prevented. Since thefirst lens component can be fixed, space surrounding the first lenscomponent can be utilized, for example, to place other members.

[0117] In the present invention, as mentioned above, the eyepiece systemis constructed with three lens components: the first lens component withpositive refracting power, the second lens component with positiverefracting power, and the third lens component with negative refractingpower. Whereby, the distance from the screen to the entrance surface ofthe first lens component of the eyepiece system is increased.

[0118] In this case, when the number of lenses constituting the eyepiecesystem is four or less, notably four, satisfactory performance issecured and cost can be reduced.

[0119] As mentioned above, when the negative refracting power of thethird lens component is strengthened to shift the position of the frontprincipal point to the object side of the eyepiece, the distance fromthe screen to the entrance surface of the first lens component of theeyepiece system is ensured as a sufficient length without increasing thefocal length.

[0120] In this case, it is desirable that, in the first and second lenscomponents to which positive refracting powers are imparted, the lenscomponents have the loads of refracting powers of nearly the same extentin order to suppress the production of aberration and satisfy thefollowing condition:

0.5<f2/f′<1.2  (14)

[0121] where f2 is the focal length of the second lens component.

[0122] Below the lower limit of Condition (14), the refracting power ofthe second lens component is strengthened and the Petzval sum isimpaired. When the second lens component is moved to make the diopteradjustment, aberration in each diopter condition fluctuates, andespecially fluctuations in spherical aberration and astigmatism areheavy. Consequently, it becomes difficult to properly correct aberrationover the whole range of diopter adjustment. Beyond the upper limit ofCondition (14), the refracting power of the second lens component isweakened and the height of the off-axis chief ray passing through thefirst lens component is increased. As a result, off-axis aberration,notably chromatic aberration of magnification, produced in the firstlens component becomes considerable, and it becomes difficult to correctsuch aberration. Since the ray height is increased, vignetting is causedby the prism and a satisfactory eye relief cannot be ensured.

[0123] It is more desirable that the lower limit of Condition (14) isset to 0.55 or 0.6 and the upper limit is 1.0 or 1.2. For example, it ismore desirable to satisfy one of the following conditions:

0.55<f2/f′<1.0  (14-1)

0.6<f2/f′<0.9  (14-2)

[0124] In order to strengthen the negative refracting power of the thirdlens component and to shift the position of the front principal point tothe object side of the eyepiece, it is favorable to satisfy thefollowing condition:

−1.3<f12/f3<−0.9  (15)

[0125] where f12 is a combined focal length of the first lens componentand the second lens component.

[0126] Below the lower limit of Condition (15), the negative refractionpower of the third lens component becomes so strong that correction foraberration is difficult. Beyond the upper limit of Condition (15), thefront principal point cannot be completely shifted to the object side ofthe eyepiece, and hence it becomes difficult to ensure the distance fromthe screen to the entrance surface of the first lens component of theeyepiece system as a sufficient length.

[0127] It is more desirable that the lower limit of Condition (15) isset to −1.25 or −1.2 and the upper limit is −0.95 or −1.0. For example,it is more desirable to satisfy one of the following conditions:

−1.25<f12/f3<−0.95  (15-1)

−1.2<f12/f3<−1.0  (15-2)

[0128] In accordance with the drawings, the embodiments of the presentinvention will be described below.

[0129]FIG. 1 shows one embodiment of a camera provided with the eyepieceof the present invention.

[0130] A camera 1 of FIG. 1 is designed so that a photographic lens 2 isinterchangeable in regard of the camera through a mount, not shown.Also, in the present invention, it is assumed that an apparatusconstructed so that, even though the photographic lens is not provided,it can be mounted, is called a camera.

[0131] In FIG. 1, reference numeral 4 represents a CCD as an electronicimage sensor. In accordance with a signal from the CCD, image processingis performed in a processing circuit, and image information is stored ina memory. In stored image information, an image is displayed by apersonal computer, not shown, and the information can be recorded andstored in various information storage media.

[0132] Reference numeral 5 denotes a quick-return mirror placed on anoptical axis 3 of the photographic lens 2 between the photographic lens2 and the CCD 4, and 6 denotes a finder screen placed on an optical pathreflected by the quick-return mirror 5. The entrance or exit side ofthis screen is constructed with a ground glass surface.

[0133] Reference numeral 7 denotes a pentagonal roof prism. Thepentagonal roof prism 7 includes, in order of an arrangement along theoptical path, a plane entrance surface 7 a, a roof reflection surface 7b, a plane reflection surface 7 c, and a plane exit surface 7 d.

[0134] Reference numeral 8 denotes an eyepiece, which is constructed inaccordance with the aspect of each of the embodiments to be describedlater. On the exit side of the eyepiece 8, a plane-parallel plate 9 isprovided as cover glass.

[0135] An emerging beam of light is introduced into a pupil 10 of anobserver and an image to be photographed is observed.

[0136] The camera of the present invention may be constructed so thatthe photographic lens 2 is integrated with a camera body and is notinterchangeable in regard of the camera.

[0137] Instead of the CCD 4, a photographing film may also be placed.

[0138] Instead of the quick-return mirror 5, a half mirror or a pathsplitting prism may be used.

[0139] In addition to the ground glass surface, the screen 6 may beconstructed with a minute-prism array surface or a hologram surface.

[0140] A surface opposite to the screen 6 may be constructed with anoptical surface having a function of converging light, such as a Fresnellens surface or a convex surface, so that a function of condensing lighton the periphery of the picture plane is improved.

[0141] In addition to the pentagonal roof prism 7, a roof mirror may beused together with a plane mirror, or a plurality of reflection surfacesfor erecting an image may be separately used.

[0142] When a prism is used for the image erecting system, opticalrefracting power is imparted to its entrance or exit surface, or a fieldlens is placed close to the screen 6. Whereby, correction for aberrationand light-condensing efficiency can be further improved.

[0143] In this case, the focal length f of the entire system is a valuein which the refracting power of the prism is taken into account. On theother hand, the air-equivalent length fb is the one from the screen 6 tothe entrance surface of a first lens component 8 a of the eyepiece 8.

[0144] The cover glass 9 may or may not be provided. When the coverglass 9 is used, the angle S refers to an angle made by the mostoff-axis chief ray passing through a point on the optical axis at adistance of 23 mm along the optical axis, over the air-equivalentlength, from the exit surface of a third lens component 8 c of theeyepiece 8 with the optical axis.

[0145] In the diopter adjustment, as in each of the embodiments to bedescribed later, only the second lens component may be moved, or aplurality of lens components may be moved.

[0146]FIGS. 2 and 3 depict various factors of the conditions in thepresent invention. FIG. 2 shows the screen 6 constructed with the groundglass surface. On or in the proximity of the screen 6, provision forlimiting a field range (for example, black painting or the mounting of afield frame) is made. Also, symbol Y denotes the diagonal length of thepicture plane in an observable range on the screen 6.

[0147]FIG. 3 illustrates the angle S. In this figure, the maximum fieldangle where the observer's pupil is located at a distance of 23 mm formthe exit surface of the third lens component is represented by S. Thatis, S is an angle made by the most off-axis chief ray passing through apoint on the optical axis at a distance of 23 mm along the optical axisfrom the exit surface of the third lens component 8 c of the eye-piece 8with the optical axis.

[0148] Instead of the screen 6, a liquid crystal display (LCD) which hasan image plane displaying an image of an object may be used as anelectronic viewfinder. In this case, image information from the CCD 4 isdisplayed on the LCD.

[0149] First Embodiment

[0150]FIG. 4 shows an optical arrangement, at a diopter of 0 m⁻¹, in thefirst embodiment of a camera provided with the eyepiece according to thepresent invention. For convenience of illustration, a plane-parallelplate-like member in FIG. 4 is shown by developing the pentagonal roofprism.

[0151] FIGS. 5A-5D, 6A-6D, and 7A-7D show aberration characteristics inthe first embodiment. Also, the diopter (m⁻¹) is taken as the axis ofabscissas relative to spherical aberration and curvature of field, andthe angle (minute) is taken as the axis of abscissas relative tochromatic aberration of magnification.

[0152] The first embodiment has the pentagonal roof prism 7 and theeyepiece system 8. The eyepiece system 8 includes, in order from theobject side, a first lens component 8 a with positive refracting powerwhich is a biconvex lens, a second lens component 8 b with positiverefracting power which is a meniscus lens with a convex surface directedtoward the object side, and a third lens component 8 c with negativerefracting power which is a biconcave lens. The diopter adjustment ismade by moving the second lens component 8 b.

[0153] Subsequently, numerical data of optical members constituting theeyepiece system of the first embodiment are shown below.

[0154] In the numerical data of the first embodiment, r₁, r₂, . . .denote radii of curvature of surfaces of individual lenses and a prism;d₁, d₂, . . . denote thicknesses of individual lenses and the prism, orair spacings between them; n_(d1), n_(d2), . . . denote refractiveindices of individual lenses and the prism at the d line; ν_(d1),ν_(d2), . . . denote Abbe's numbers of individual lenses and the prism;and fl denotes the focal length of the entire system from the screen tothe exit surface of the eyepiece.

[0155] Also, these symbols are also used for the numerical data of otherembodiments to be described later.

[0156] Numerical Data 1 Diopter (m⁻¹) = +1 ˜ 0 ˜ −3 fl (mm) = 47.62 ˜50.00 ˜ 60.75 Pupil diameter (mm) = 8 Diagonal length Y (or Y′) (mm) =22.2 r₁ = ∞ d₁ = 2.50 r₂ = ∞ d₂ = 82.40 n_(d2) = 1.51633 υ_(d2) = 64.14r₃ = ∞ d₃ = 9.00 r₄ = 69.592 d₄ = 4.95 n_(d4) = 1.62041 υ_(d4) = 60.29r₅ = −48.494 d₅ = D5 r₆ = 21.408 d₆ = 5.07 n_(d6) = 1.77250 υ_(d6) =49.60 r₇ = 51.041 d₇ = D7 r₈ = −436.870 d₈ = 1.50 n_(d8) = 1.80518υ_(d8) = 25.42 r₉ = 21.601 d₉ = 23.00 r₁₀ = Pupil Diopter (m⁻¹) = +1 ˜ 0˜ −3 D5 1.000 1.655 4.073 D7 4.073 3.417 1.000

[0157] Second Embodiment

[0158]FIG. 8 shows an optical arrangement, at a diopter of 0 m⁻¹, in thesecond embodiment of the eyepiece system according to the presentinvention. For convenience of illustration, a plane-parallel plate-likemember in FIG. 8 is shown by developing the pentagonal roof prism.

[0159] FIGS. 9A-9D, 10A-10D, and 11A-11D show aberration characteristicsin the second embodiment. Also, the diopter (m⁻¹) is taken as the axisof abscissas relative to spherical aberration and curvature of field,and the angle (minute) is taken as the axis of abscissas relative tochromatic aberration of magnification.

[0160] The second embodiment has the pentagonal roof prism 7 and theeyepiece system 8. The eyepiece system 8 includes, in order from theobject side, the first lens component 8 a with positive refracting powerwhich is a biconvex lens, the second lens component 8 b with positiverefracting power which is a meniscus lens with a convex surface directedtoward the object side, and the third lens component 8 c with negativerefracting power which is a biconcave lens. The diopter adjustment ismade by moving the second lens component 8 b.

[0161] Subsequently, numerical data of optical members constituting theeyepiece system of the second embodiment are shown below.

[0162] Numerical Data 2 Diopter (m⁻¹) = +1 ˜ 0 ˜ −3 fl (mm) = 52.41 ˜55.57 ˜ 71.04 Pupil diameter (mm) = 8 Diagonal length Y (or Y′) (mm) =22.2 r₁ = ∞ d₁ = 2.50 r₂ = ∞ d₂ = 82.40 n_(d2) = 1.51633 υ_(d2) = 64.14r₃ = ∞ d₃ = 14.00 r₄ = 92.341 d₄ = 4.44 n_(d4) = 1.60311 υ_(d4) = 60.64r₅ = −48.162 d₅ = D5 r₆ = 26.069 d₆ = 4.79 n_(d6) = 1.60311 υ_(d6) =60.64 r₇ = 96.770 d₇ = D7 r₈ = −103.060 d₈ = 1.50 n_(d8) = 1.805189υ_(d8) = 25.42 r₉ = 38.122 d₉ = 23.00 r₁₀ = Pupil Diopter (m⁻¹) = +1 ˜ 0˜ −3 D5 1.000 2.180 6.717 D7 6.717 5.537 1.000

[0163] Third Embodiment

[0164]FIG. 12 shows an optical arrangement, at a diopter of 0 m⁻¹, inthe third embodiment of the eyepiece system according to the presentinvention. For convenience of illustration, a plane-parallel plate-likemember in FIG. 12 is shown by developing the pentagonal roof prism.

[0165] FIGS. 13A-13D, 14A-14D, and 15A-15D show aberrationcharacteristics in the third embodiment. Also, the diopter (m⁻¹) istaken as the axis of abscissas relative to spherical aberration andcurvature of field, and the angle (minute) is taken as the axis ofabscissas relative to chromatic aberration of magnification.

[0166] The third embodiment has the pentagonal roof prism 7 and theeyepiece system 8. The eyepiece system 8 includes, in order from theobject side, the first lens component 8 a with positive refracting powerwhich is a biconvex lens, the second lens component 8 b with positiverefracting power which is a cemented lens of a biconvex lens element 8 b₁ and a concave meniscus lens element 8 b ₂, with a convex surfacedirected toward the object side, and the third lens component 8 c withnegative refracting power which is a concave meniscus lens. The diopteradjustment is made by moving the second lens component 8 b.

[0167] Subsequently, numerical data of optical members constituting theeyepiece system of the third embodiment are shown below.

[0168] Numerical Data 3 Diopter (m⁻¹) = +1 ˜ 0 ˜ −3 fl (mm) = 47.18 ˜50.00 ˜ 63.63 Pupil diameter (mm) = 8 Diagonal length Y (or Y′) (mm) =22.2 r₁ = ∞ d₁ = 3.00 r₂ = ∞ d₂ = 86.00 n_(d2) = 1.51633 υ_(d2) = 64.14r₃ = ∞ d₃ = 6.95 r₄ = 48.639 d₄ = 4.60 n_(d4) = 1.51633 υ_(d4) = 64.14r₅ = −123.366 d₅ = D5 r₆ = 27.357 d₆ = 7.90 n_(d6) = 1.58913 υ_(d6) =61.14 r₇ = −32.073 d₇ = 1.50 n_(d7) = 1.80518 υ_(d7) = 25.42 r₈ =−154.705 d₈ = D8 r₉ = 166.986 d₉ = 1.50 n_(d9) = 1.48749 υ_(d9) = 70.23r₁₀ = 16.259 d₁₀ = 23.00 r₁₁ = Pupil Diopter (m⁻¹) = +1 ˜ 0 ˜ 3 D5 1.0002.303 7.246 D7 7.246 5.943 1.000

[0169] Numerical values of the conditions in the first to thirdembodiments are listed in Table 1. TABLE 1 Conditions 1st embodiment 2ndembodiment 3rd embodiment (1) 0.255 0.202 0.224 (2) 2.97 3.19 3.00 (7)−0.51 −0.62 −0.74 (5) (mm) 22.2 22.2 22.2

[0170] Also, the first to third embodiments are designed on theassumption that the exit pupil is formed at a distance of 23 mm from thelast lens surface of the eyepiece.

[0171] Values of the factors of the conditions are as shown in Table 2.TABLE 2 1st embodiment 2nd embodiment 3rd embodiment S  12.7°  11.4° 12.6° fb (f′b) 65.94 mm 70.82 mm  66.6 mm Y (Y′)  22.2 mm  22.2 mm 22.2 mm f3  25.5 mm 34.45 mm  37.0 mm f(f″) 50.00 mm 55.57 mm 50.00 mm

[0172] Fourth Embodiment

[0173]FIG. 16 shows an optical arrangement, at a diopter of −0.5 m⁻¹, inthe fourth embodiment of the eyepiece system according to the presentinvention. For convenience of illustration, a plane-parallel plate-likemember in FIG. 16 is shown by developing the pentagonal roof prism.

[0174] FIGS. 17A-17D, 18A-18D, and 19A-19D show aberrationcharacteristics in the fourth embodiment. Also, the diopter (m⁻¹) istaken as the axis of abscissas relative to spherical aberration andcurvature of field, and the angle (minute) is taken as the axis ofabscissas relative to chromatic aberration of magnification.

[0175] The fourth embodiment has the pentagonal roof prism 7 and theeyepiece system 8. The eyepiece system 8 includes, in order from theobject side, the first lens component 8 a with positive refracting powerwhich is a positive biconvex lens, the second lens component 8 b withpositive refracting power which is a single positive meniscus lens witha convex surface directed toward the object side, and the third lenscomponent 8 c with negative refracting power which is a negativebiconcave lens. The diopter adjustment is made by moving the second lenscomponent 8 b.

[0176] Subsequently, numerical data of optical members constituting theeyepiece system of the fourth embodiment are shown below.

[0177] Numerical Data 4 Diopter (m⁻¹) = +1 ˜ −0.5 ˜ −3 fl (mm) = 47.05 ˜50.02 ˜ 56.99 Pupil diameter (mm) = 8 Diagonal length Y (or Y′) (mm) =21.9 fb′ = 1.4 f′ r₁ = ∞ d₁ = 3.50 r₂ = ∞ d₂ = 80.38 n_(d2) = 1.51633υ_(d2) = 64.14 r₃ = ∞ d₃ = 13.63 r₄ = 36.997 d₄ = 6.45 n_(d4) = 1.60311υ_(d4) = 60.64 r₅ = −60.534 d₅ = D5 r₆ = 15.951 d₆ = 4.02 n_(d6) =1.60311 υ_(d6) = 60.64 r₇ = 47.972 d₇ = D7 r₈ = −448.012 d₈ = 1.50n_(d8) = 1.80518 υ_(d8) = 25.42 r₉ = 15.260 d₉ = 23.00 r₁₀ = PupilDiopter (m⁻¹) = +1 ˜ −0.5 ˜ −3 D5 1.07 1.61 2.70 D7 3.46 2.92 1.83

[0178] Fifth Embodiment

[0179]FIG. 20 shows an optical arrangement, at a diopter of −0.5 m⁻¹, inthe fifth embodiment of the eyepiece system according to the presentinvention. For convenience of illustration, a plane-parallel plate-likemember in FIG. 20 is shown by developing the pentagonal roof prism.

[0180] FIGS. 21A-21D, 22A-22D, and 23A-23D show aberrationcharacteristics in the fifth embodiment. Also, the diopter (m⁻¹) istaken as the axis of abscissas relative to spherical aberration andcurvature of field, and the angle (minute) is taken as the axis ofabscissas relative to chromatic aberration of magnification.

[0181] The fifth embodiment has the pentagonal roof prism 7 and theeyepiece system 8. The eyepiece system 8 includes, in order from theobject side, the first lens component 8 a with positive refracting powerwhich is a positive biconvex lens, the second lens component 8 b withpositive refracting power which is a single positive meniscus lens witha convex surface directed toward the object side, and a third lenscomponent 8 c′ which is a cemented lens of a positive biconvex lenselement and a negative biconcave lens element, having negativerefracting power as a whole. The diopter adjustment is made by movingthe second lens component 8 b.

[0182] Subsequently, numerical data of optical members constituting theeyepiece system of the fifth embodiment are shown below.

[0183] Numerical Data 5 Diopter (m⁻¹) = +1 ˜ −0.5 ˜ −3 fl (mm) = 47.84 ˜50.80 ˜ 57.76 Pupil diameter (mm) = 8 Diagonal length Y (or Y′) (mm) =21.9 fb′ = 1.4 f′ r₁ = ∞ d₁ = 4.50 r₂ = ∞ d₂ = 80.38 n_(d2) = 1.51633υ_(d2) = 64.14 r₃ = ∞ d₃ = 16.14 r₄ = 27.127 d₄ = 6.89 n_(d4) = 1.48749υ_(d4) = 70.23 r₅ = −73.436 d₅ = D5 r₆ = 16.252 d₆ = 3.13 n_(d6) =1.69680 υ_(d6) = 55.53 r₇ = 37.375 d₇ = D7 r₈ = 118.048 d₈ = 2.57 n_(d8)= 1.69680 υ_(d8) = 55.53 r₉ = −24.798 d₉ = 1.00 n_(d9) = 1.80610 υ_(d9)= 40.92 r₁₀ = 14.528 d₁₀ = 23.00 r₁₁ = Pupil Diopter (m⁻¹) = +1 ˜ −0.5 ˜−3 D5 1.00 1.56 2.69 D7 3.44 2.88 1.75

[0184] Sixth Embodiment

[0185]FIG. 24 shows an optical arrangement, at a diopter of −0.5 m⁻¹, inthe sixth embodiment of the eyepiece system according to the presentinvention. For convenience of illustration, a plane-parallel plate-likemember in FIG. 24 is shown by developing the pentagonal roof prism.

[0186] FIGS. 25A-25D, 26A-26D, and 27A-27D show aberrationcharacteristics in the sixth embodiment. Also, the diopter (m⁻¹) istaken as the axis of abscissas relative to spherical aberration andcurvature of field, and the angle (minute) is taken as the axis ofabscissas relative to chromatic aberration of magnification.

[0187] The sixth embodiment has the pentagonal roof prism 7 and theeyepiece system 8. The eyepiece system 8 includes, in order from theobject side, the first lens component 8 a with positive refracting powerwhich is a positive biconvex lens, the second lens component 8 b withpositive refracting power which is a single positive meniscus lens witha convex surface directed toward the object side, and the third lenscomponent 8 c′ which is a cemented lens of a positive biconvex lenselement and a negative biconcave lens element, having negativerefracting power as a whole. The diopter adjustment is made by movingthe second lens component 8 b.

[0188] Subsequently, numerical data of optical members constituting theeyepiece system of the sixth embodiment are shown below.

[0189] Numerical Data 6 Diopter (m⁻¹) = +1 ˜ −0.5 ˜ −3 fl (mm) = 47.80 ˜50.81 ˜ 57.97 Pupil diameter (mm) = 8 Diagonal length Y (or Y′) (mm) =21.9 fb′ = 1.4 f′ r₁ = ∞ d₁ = 4.50 r₂ = ∞ d₂ = 80.38 n_(d2) = 1.51633υ_(d2) = 64.14 r₃ = ∞ d₃ = 16.14 r₄ = 30.040 d₄ = 6.09 n_(d4) = 1.48749υ_(d4) = 70.23 r₅ = −61.367 d₅ = D5 r₆ = 18.892 d₆ = 3.20 n_(d6) =1.69680 υ_(d6) = 55.53 r₇ = 45.924 d₇ = D7 r₈ = 187.857 d₈ = 3.00 n_(d8)= 1.69680 υ_(d8) = 55.53 r₉ = −22.241 d₉ = 2.04 n_(d9) = 1.80610 υ_(d9)= 40.92 r₁₀ = 16.819 d₁₀ = 23.00 r₁₁ = Pupil Diopter (m⁻¹) = +1 ˜ −0.5 ˜−3 D5 1.00 1.69 3.06 D7 3.82 3.13 1.76

[0190] Seventh Embodiment

[0191]FIG. 28 shows an optical arrangement, at a diopter of −0.5 m⁻¹, inthe seventh embodiment of the eyepiece system according to the presentinvention. For convenience of illustration, a plane-parallel plate-likemember in FIG. 28 is shown by developing the pentagonal roof prism.

[0192] FIGS. 29A-29D, 30A-30D, and 31A-31D show aberrationcharacteristics in the seventh embodiment. Also, the diopter (m⁻¹) istaken as the axis of abscissas relative to spherical aberration andcurvature of field, and the angle (minute) is taken as the axis ofabscissas relative to chromatic aberration of magnification.

[0193] The seventh embodiment has the pentagonal roof prism 7 and theeyepiece system 8. The eyepiece system 8 includes, in order from theobject side, a first lens component 8 a′ in which a negative meniscuslens with a convex surface directed toward the object side is cementedto a positive biconvex lens, having positive refracting power as awhole, the second lens component 8 b with positive refracting powerwhich is a single positive meniscus lens with a convex surface directedtoward the object side, and a third lens component 8 c″ with negativerefracting power which is a negative meniscus lens with a convex surfacedirected toward the object side. The diopter adjustment is made bymoving the second lens component 8 b.

[0194] Subsequently, numerical data of optical members constituting theeyepiece system of the seventh embodiment are shown below.

[0195] Numerical Data 7 Diopter (m⁻¹) = +1 ˜ −0.5 ˜ −3 fl (mm) = 47.86 ˜50.80 ˜ 57.70 Pupil diameter (mm) = 8 Diagonal length Y (or Y′) (mm) =21.9 fb′ = 1.4 f′ r₁ = ∞ d₁ = 4.50 r₂ = ∞ d₂ = 80.38 n_(d2) = 1.51633υ_(d2) = 64.14 r₃ = ∞ d₃ = 16.14 r₄ = 34.412 d₄ = 2.00 n_(d4) = 1.72825υ_(d4) = 28.46 r₅ = 18.219 d₅ = 6.90 n_(d5) = 1.69680 υ_(d5) = 55.53 r₆= −93.287 d₆ = D6 r₇ = 17.624 d₇ = 3.05 n_(d5) = 1.80610 υ_(d5) = 40.92r₈ = 32.403 d₈ = D8 r₉ = 229.785 d₉ = 2.00 n_(d9) = 1.80610 υ_(d9) =40.92 r₁₀ = 14.411 d₁₀ = 23.00 r₁₁ = Pupil Diopter (m⁻¹) = +1 ˜ −0.5 ˜−3 D5 1.00 1.62 2.87 D7 4.27 3.65 2.40

[0196] Eighth Embodiment

[0197]FIG. 32 shows an optical arrangement, at a diopter of −0.5 m⁻¹, inthe eighth embodiment of the eyepiece system according to the presentinvention. For convenience of illustration, a plane-parallel plate-likemember in FIG. 32 is shown by developing the pentagonal roof prism.

[0198] FIGS. 33A-33D, 34A-34D, and 35A-35D show aberrationcharacteristics in the eighth embodiment. Also, the diopter (m⁻¹) istaken as the axis of abscissas relative to spherical aberration andcurvature of field, and the angle (minute) is taken as the axis ofabscissas relative to chromatic aberration of magnification.

[0199] The eighth embodiment has the pentagonal roof prism 7 and theeyepiece system 8. The eyepiece system 8 includes, in order from theobject side, the first lens component 8 a with positive refracting powerwhich is a positive biconvex lens, the second lens component 8 b withpositive refracting power which is a single positive meniscus lens witha convex surface directed toward the object side, and the third lenscomponent 8 c′ which is a cemented lens of a positive biconvex lenselement and a negative biconcave lens element, having negativerefracting power as a whole. The diopter adjustment is made by movingthe second lens component 8 b.

[0200] Subsequently, numerical data of optical members constituting theeyepiece system of the eighth embodiment are shown below.

[0201] Numerical Data 8 Diopter (m⁻¹) = +1 ˜ −0.5 ˜ −3 fl (mm) = 47.55 ˜50.38 ˜ 57.02 Pupil diameter (mm) = 8 Diagonal length Y (or Y′) (mm) =21.9 fb′= 1.4 f′ r₁ = ∞ d₁ = 4.50 r₂ = ∞ d₂ = 80.38 n_(d2) = 1.51633υ_(d2) = 64.14 r₃ = ∞ d₃ = 16.14 r₄ = 31.782 d₄ = 7.50 n_(d4) = 1.49700υ_(d4) = 81.54 r₅ = −65.303 d₅ = D5 r₆ = 15.563 d₆ = 3.71 n_(d6) =1.69680 υ_(d6) = 55.53 r₇ = 44.319 d₇ = D7 r₈ = 106.618 d₈ = 2.50 n_(d8)= 1.69680 υ_(d8) = 55.53 r₉ = −30.748 d₉ = 1.00 n_(d9) = 1.80610 υ_(d9)= 40.92 r₁₀ = 12.778 d₁₀ = 23.00 r₁₁ = Pupil Diopter (m⁻¹) = +1 ˜ −0.5 ˜−3 D5 1.07 1.51 2.39 D7 2.82 2.38 1.50

[0202] Numerical values of the conditions in the fourth to eighthembodiments are listed in Table 3. TABLE 3 Conditions 4th embodiment 5thembodiment 6th embodiment 7th embodiment 8th embodiment  (8) 3.21 3.373.37 3.37 3.37  (9) −0.36 −0.37 −0.40 −0.38 −0.33 (10) 0.78 0.82 0.830.75 0.88 (13) 21.9 21.9 21.9 21.9 21.9

[0203] Values of the factors of the conditions in the fourth to eighthembodiments are shown in Table 4. TABLE 4 Conditions 4th embodiment 5thembodiment 6th embodiment 7th embodiment 8th embodiment f (f″) 50.0250.80 50.81 50.80 50.38 f1 39.25 41.57 42.29 38.21 44.15 f2 36.83 38.943.93 43.9 32.69 f3 −18.06 −18.72 −20.47 −19.15 −16.85 f12 19.79 21.0622.2 21.4 19.77 fb′ (f′b′) 70.15 73.65 73.65 73.65 73.65 Y (Y′) 21.8821.88 21.88 21.88 21.88

What is claimed is:
 1. A single-lens reflex camera comprising: a screenon which an image of an object is projected; a plurality of reflectionsurfaces for erecting the image on the screen; and an eyepiece systemwith positive refracting power for observing the image, wherein theeyepiece system comprises, in order from an object side, a first lenscomponent with positive refracting power, a second lens component withpositive refracting power, and a third lens component with negativerefracting power so that spacings between the first lens component andthe second lens component and between the second lens component and thethird lens component are changed to thereby make a diopter adjustment,and the single-lens reflex camera satisfies the following conditions:0.15<tan(S)<0.352.00<fb/Y<4.00−0.80<f3/f<−0.40 where S is an angle, at adiopter of 0 m⁻¹, made by a most off-axis chief ray passing through apoint on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;fb is an air-equivalent length, at a diopter of 0 m⁻¹, from the screento an entrance surface of the first lens component; Y is a diagonallength of a picture plane on the screen; f3 is a focal length of thethird lens component; and f is a focal length, at a diopter of 0 m⁻¹, ofan entire system from the screen to an exit surface of the eyepiecesystem.
 2. A single-lens reflex camera comprising: a screen on which animage of an object is projected; a plurality of reflection surfaces forerecting the image on the screen, and an eyepiece system with positiverefracting power for observing the image, wherein the eyepiece systemcomprises, in order from an object side, a first lens component withpositive refracting power, a second lens component with positiverefracting power, and a third lens component with negative refractingpower so that spacings between the first lens component and the secondlens component and between the second lens component and the third lenscomponent are changed to thereby make a diopter adjustment, and thesingle-lens reflex camera satisfies the following condition:0.15<tan(S)<0.35−0.65<f3/f<−0.45 where S is an angle, at a diopter of 0m⁻¹, made by a most off-axis chief ray passing through a point on anoptical axis at a distance of 23 mm along the optical axis from an exitsurface of the third lens component with the optical axis; f3 is a focallength of the third lens component; and f is a focal length, at adiopter of 0 m⁻¹, of an entire system from the screen to an exit surfaceof the eyepiece system.
 3. A single-lens reflex camera comprising: ascreen on which an image of an object is projected; a plurality ofreflection surfaces for erecting the image on the screen, and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power, and a third lens componentwith negative refracting power so that spacings between the first lenscomponent and the second lens component and between the second lenscomponent and the third lens component are changed to thereby make adiopter adjustment, and the single-lens reflex camera satisfies thefollowing condition: 0.15<tan(S)<0.3515 mm<Y<30 mm where S is an angle,at a diopter of 0 m⁻¹, made by a most off-axis chief ray passing througha point on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;and Y is a diagonal length of a picture plane on the screen.
 4. Asingle-lens reflex camera comprising: a screen on which an image of anobject is projected; a plurality of reflection surfaces for erecting theimage on the screen; and an eyepiece system with positive refractingpower for observing the image, wherein the eyepiece system comprises, inorder from an object side, a first lens component with positiverefracting power, a second lens component with positive refractingpower, and a third lens component with negative refracting power so thatspacings between the first lens component and the second lens componentand between the second lens component and the third lens component arechanged to thereby make a diopter adjustment, and the single-lens reflexcamera satisfies the following conditions:0.15<tan(S)<0.352.70<fb/Y<3.20−0.80<f3/f<−0.30 where S is an angle, at adiopter of 0 m⁻¹, made by a most off-axis chief ray passing through apoint on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;fb is an air-equivalent length, at a diopter of 0 m⁻¹, from the screento an entrance surface of the first lens component; Y is a diagonallength of a picture plane on the screen; f3 is a focal length of thethird lens component; and f is a focal length, at a diopter of 0 m⁻¹, ofan entire system from the screen to an exit surface of the eyepiecesystem.
 5. A single-lens reflex camera according to claim 1 or 2,wherein each of the first lens component, the second lens component, andthe third lens component consist of a single lens or a cemented lens. 6.A single-lens reflex camera according to claim 1 or 2, wherein only thesecond lens component is moved and thereby the diopter adjustment ismade.
 7. A single-lens reflex camera according to claim 1, furthersatisfying the following condition: 15 mm<Y<30 mm
 8. A single-lensreflex camera comprising: a screen on which an image of an object isprojected; a plurality of reflection surfaces for erecting the image onthe screen; and an eyepiece system with positive refracting power forobserving the image, wherein the eyepiece system comprises, in orderfrom an object side, a first lens component with positive refractingpower, a second lens component with positive refracting power, and athird lens component with negative refracting power so that spacingsbetween the first lens component and the second lens component andbetween the second lens component and the third lens component arechanged to thereby make a diopter adjustment, and the single-lens reflexcamera satisfies the following conditions:0.15<tan(S)<0.352.70<fb/Y<3.20−0.80<f3/f<−0.40 where S is an angle, at adiopter of 0 m⁻¹, made by a most off-axis chief ray passing through apoint on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;fb is an air-equivalent length, at a diopter of 0 m⁻¹, from the screento an entrance surface of the first lens component; Y is a diagonallength of a picture plane on the screen; f3 is a focal length of thethird lens component; and f is a focal length, at a diopter of 0 m⁻¹, ofan entire system from the screen to an exit surface of the eyepiecesystem.
 9. A single-lens reflex camera comprising: a screen on which animage of an object is projected; a plurality of reflection surfaces forerecting the image on the screen; and an eyepiece system with positiverefracting power for observing the image, wherein the eyepiece systemcomprises, in order from an object side, a first lens component withpositive refracting power, a second lens component with positiverefracting power, and a third lens component with negative refractingpower so that spacings between the first lens component and the secondlens component and between the second lens component and the third lenscomponent are changed to thereby make a diopter adjustment, and thesingle-lens reflex camera satisfies the following conditions:0.15<tan(S)<0.352.00<fb/Y<4.00−0.65<f3/f<−0.45 where S is an angle, at adiopter of 0 m⁻¹, made by a most off-axis chief ray passing through apoint on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;fb is an air-equivalent length, at a diopter of 0 m⁻¹, from the screento an entrance surface of the first lens component; Y is a diagonallength of a picture plane on the screen; f3 is a focal length of thethird lens component; and f is a focal length, at a diopter of 0 m⁻¹, ofan entire system from the screen to an exit surface of the eyepiecesystem.
 10. A single-lens reflex camera comprising: a screen on which animage of an object is projected; a plurality of reflection surfaces forerecting the image on the screen; and an eyepiece system with positiverefracting power for observing the image, wherein the eyepiece systemcomprises, in order from an object side, a first lens component withpositive refracting power, a second lens component with positiverefracting power, and a third lens component with negative refractingpower so that spacings between the first lens component and the secondlens component and between the second lens component and the third lenscomponent are changed to thereby make a diopter adjustment, and thesingle-lens reflex camera satisfies the following conditions:0.15<tan(S)<0.352.00<fb/Y<4.00−0.65<f3/f<−0.50 where S is an angle, at adiopter of 0 m⁻¹, made by a most off-axis chief ray passing through apoint on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;fb is an air-equivalent length, at a diopter of 0 m⁻¹, from the screento an entrance surface of the first lens component; Y is a diagonallength of a picture plane on the screen; f3 is a focal length of thethird lens component; and f is a focal length, at a diopter of 0 m⁻¹, ofan entire system from the screen to an exit surface of the eyepiecesystem.
 11. A single-lens reflex camera according to claim 2, furthersatisfying the following condition: 15 mm<Y<30 mm where Y is a diagonallength of a picture plane on the screen.
 12. A single-lens reflex cameraaccording to claim 3, further satisfying the following condition:2.00<fb/Y<4.00 where fb is an air-equivalent length, at a diopter of 0m⁻¹, from the screen to an entrance surface of the first lens component.13. A single-lens reflex camera according to claim 3, further satisfyingthe following condition: 2.70<fb/Y<3.20 where fb is an air-equivalentlength, at a diopter of 0 m⁻¹, from the screen to an entrance surface ofthe first lens component.
 14. A single-lens reflex camera according toclaim 4, further satisfying the following condition: 15 mm<Y<30 mm
 15. Asingle-lens reflex camera comprising: a screen on which an image of anobject is projected; a plurality of reflection surfaces for erecting theimage on the screen; and an eyepiece system with positive refractingpower for observing the image, wherein the eyepiece system comprises, inorder from an object side, a first lens component with positiverefracting power, a second lens component with positive refractingpower, and a third lens component with negative refracting power so thatspacings between the first lens component and the second lens componentand between the second lens component and the third lens component arechanged to thereby make a diopter adjustment, and the single-lens reflexcamera satisfies the following conditions:0.15<tan(S)<0.352.70<fb/Y<3.20−0.80<f3/f<−0.40 where S is an angle, at adiopter of 0 m⁻¹, made by a most off-axis chief ray passing through apoint on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;fb is an air-equivalent length, at a diopter of 0 m⁻¹, from the screento an entrance surface of the first lens component; Y is a diagonallength of a picture plane on the screen; f3 is a focal length of thethird lens component; and f is a focal length, at a diopter of 0 m⁻¹, ofan entire system from the screen to an exit surface of the eyepiecesystem.
 16. A single-lens reflex camera according to claim 5, whereinthe first lens component is configured into a biconvex shape, the secondlens component is configured into a meniscus shape with a convex surfacedirected toward the object side or a biconvex shape, and the third lenscomponent is configured into a shape such that a pupil-side surface issmaller in an absolute value of a radius of curvature than anobject-side surface.
 17. A single-lens reflex camera according to claim5, wherein the first lens component is configured into a biconvex shape,the second lens component consists of a cemented lens of a positive lenselement and a negative lens element and is configured into a shape witha convex surface directed toward the object side, and the third lenscomponent is configured into a shape such that a pupil-side surface issmaller in an absolute value of a radius of curvature than anobject-side surface.
 18. A single-lens reflex camera comprising: ascreen on which an image of an object is projected; a plurality ofreflection surfaces for erecting the image on the screen; and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power, and a third lens componentwith negative refracting power, and the single-lens reflex camerasatisfies the following conditions:2.5<fb′/Y<4.0−1.0<f3/f′<−0.20.4<f1/f′<0.95 where fb′ is anair-equivalent length, at a diopter of −0.5 (m⁻¹), from the screen to anentrance surface of the first lens component; Y is a diagonal length ofa picture plane on the screen; f3 is a focal length of the third lenscomponent; f1 is a focal length of the first lens component, and f′ is afocal length of an entire system from the screen to an exit surface ofthe eyepiece system at a diopter of −0.5 (m⁻¹).
 19. A single-lens reflexcamera comprising: a screen on which an image of an object is projected;a plurality of reflection surfaces for erecting the image on the screen;and an eyepiece system with positive refracting power for observing theimage, wherein the eyepiece system comprises, in order from an objectside, a first lens component with positive refracting power, a secondlens component with positive refracting power consisting of a singlemeniscus lens element with a convex surface directed toward the objectside, and a third lens component with negative refracting power as awhole in which a pupil-side surface is stronger in refracting power thanan object-side surface, and the single-lens reflex camera satisfies thefollowing conditions: 2.5<fb′/Y<4.0−1.0<f3/f′<−0.20.4<f1/f′<0.95 wherefb′ is an air-equivalent length, at a diopter of −0.5 (m⁻¹), from thescreen to an entrance surface of the first lens component; Y is adiagonal length of a picture plane on the screen; f3 is a focal lengthof the third lens component; f1 is a focal length of the first lenscomponent, and f′ is a focal length of an entire system from the screento an exit surface of the eyepiece system at a diopter of −0.5 (m⁻¹).20. A single-lens reflex camera comprising: a screen on which an imageof an object is projected; a plurality of reflection surfaces forerecting the image on the screen; and an eyepiece system with positiverefracting power for observing the image, wherein the eyepiece systemcomprises, in order from an object side, a first lens component withpositive refracting power, a second lens component with positiverefracting power consisting of a single meniscus lens element with aconvex surface directed toward the object side, and a third lenscomponent with negative refracting power as a whole in which apupil-side surface is stronger in refracting power than an object-sidesurface, and the single-lens reflex camera satisfies the followingconditions: 2.5<fb′/Y<4.00.4<f1/f′<0.95 where fb′ is an air-equivalentlength, at a diopter of −0.5 (m⁻¹), from the screen to an entrancesurface of the first lens component; Y is a diagonal length of a pictureplane on the screen; f1 is a focal length of the first lens component,and f′ is a focal length of an entire system from the screen to an exitsurface of the eyepiece system at a diopter of −0.5 (m⁻¹).
 21. Asingle-lens reflex camera comprising: a screen on which an image of anobject is projected; a plurality of reflection surfaces for erecting theimage on the screen; and an eyepiece system with positive refractingpower for observing the image, wherein the eyepiece system comprises, inorder from an object side, a first lens component with positiverefracting power, a second lens component with positive refracting powerconsisting of a single meniscus lens element with a convex surfacedirected toward the object side, and a third lens component withnegative refracting power as a whole in which a pupil-side surface isstronger in refracting power than an object-side surface, and thesingle-lens reflex camera satisfies the following conditions:−1.0<f3/f′<−0.20.4<f1/f′<0.95 where f3 is a focal length of the thirdlens component; f1 is a focal length of the first lens component, and f′is a focal length of an entire system from the screen to an exit surfaceof the eyepiece system at a diopter of −0.5 (m⁻¹).
 22. A single-lensreflex camera comprising: a screen on which an image of an object isprojected; a plurality of reflection surfaces for erecting the image onthe screen; and an eyepiece system with positive refracting power forobserving the image, wherein the eyepiece system comprises, in orderfrom an object side, a first lens component with positive refractingpower, a second lens component with positive refracting power consistingof a single meniscus lens element with a convex surface directed towardthe object side, and a third lens component with negative refractingpower as a whole in which a pupil-side surface is stronger in refractingpower than an object-side surface, and the single-lens reflex camerasatisfies the following conditions: 0.4<f1/f′<0.95 where f1 is a focallength of the first lens component and f′ is a focal length of an entiresystem from the screen to an exit surface of the eyepiece system at adiopter of −0.5 (m⁻¹).
 23. A single-lens reflex camera according toclaim 18 or 19, further satisfying the following condition: 16.0<Y<28.024. A single-lens reflex camera according to claim 18 or 19, furthersatisfying the following condition: 0.5<f2/f′<1.2 where f2 is a focallength of the second lens component.
 25. A single-lens reflex cameraaccording to claim 18 or 19, further satisfying the following condition:−1.3<f12/f3<−0.9 where f12 is a combined focal length of the first lenscomponent and the second lens component.
 26. A single-lens reflex cameraaccording to claim 18 or 19, wherein the first lens component comprisesa positive lens element with an Abbe's number of at least
 80. 27. Asingle-lens reflex camera according to claim 18 or 19, wherein thesecond lens component is moved along an optical axis and thereby adiopter adjustment is made.
 28. A single-lens reflex camera according toclaim 18 or 19, the second lens component or the third lens componentconsists of a cemented lens.
 29. A single-lens reflex camera accordingto claim 18 or 19, wherein the eyepiece system consists of four lenselements.
 30. A camera comprising: a plurality of reflection surfacesfor erecting an image on an image plane; and an eyepiece system withpositive refracting power for observing the image, wherein the eyepiecesystem comprises, in order from an object side, a first lens componentwith positive refracting power, a second lens component with positiverefracting power, and a third lens component with negative refractingpower so that spacings between the first lens component and the secondlens component and between the second lens component and the third lenscomponent are changed to thereby make a diopter adjustment, and thecamera satisfies the following conditions:0.15<tan(S)<0.352.00<f′b/Y′<4.00−0.80<f3/f″<−0.40 where S is an angle,at a diopter of 0 m⁻¹, made by a most off-axis chief ray passing througha point on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;f′b is an air-equivalent length, at a diopter of 0 m⁻¹, from the imageplane to an entrance surface of the first lens component; Y′ is adiagonal length of a picture plane on the image plane; f3 is a focallength of the third lens component; and f″ is a focal length, at adiopter of 0 m⁻¹, of an entire system from the image plane to an exitsurface of the eyepiece system.
 31. A camera comprising: a plurality ofreflection surfaces for erecting an image on an image plane; and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power, and a third lens componentwith negative refracting power so that spacings between the first lenscomponent and the second lens component and between the second lenscomponent and the third lens component are changed to thereby make adiopter adjustment, and the camera satisfies the following conditions:0.15<tan(S)<0.35−0.65<f3/f″<−0.45 where S is an angle, at a diopter of 0m⁻¹, made by a most off-axis chief ray passing through a point on anoptical axis at a distance of 23 mm along the optical axis from an exitsurface of the third lens component with the optical axis; f3 is a focallength of the third lens component; and f″ is a focal length, at adiopter of 0 m⁻¹, of an entire system from the image plane to an exitsurface of the eyepiece system.
 32. A camera comprising: a plurality ofreflection surfaces for erecting an image on an image plane; and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power, and a third lens componentwith negative refracting power so that spacings between the first lenscomponent and the second lens component and between the second lenscomponent and the third lens component are changed to thereby make adiopter adjustment, and the single-lens reflex camera satisfies thefollowing conditions: 0.15<tan(S)<0.3515 mm<Y′<30 mm where S is anangle, at a diopter of 0 m⁻¹, made by a most off-axis chief ray passingthrough a point on an optical axis at a distance of 23 mm along theoptical axis from an exit surface of the third lens component with theoptical axis; and Y′ is a diagonal length of a picture plane on theimage plane.
 33. A camera comprising: a plurality of reflection surfacesfor erecting an image on an image plane; and an eyepiece system withpositive refracting power for observing the image, wherein the eyepiecesystem comprises, in order from an object side, a first lens componentwith positive refracting power, a second lens component with positiverefracting power, and a third lens component with negative refractingpower so that spacings between the first lens component and the secondlens component and between the second lens component and the third lenscomponent are changed to thereby make a diopter adjustment, and thecamera satisfies the following conditions:0.15<tan(S)<0.352.70<f′b/Y′<3.20−0.80<f3/f″<−0.30 where S is an angle,at a diopter of 0 m⁻¹, made by a most off-axis chief ray passing througha point on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;f′b is an air-equivalent length, at a diopter of 0 m⁻¹, from the imageplane to an entrance surface of the first lens component; Y′ is adiagonal length of a picture plane on the image plane; f3 is a focallength of the third lens component; and f″ is a focal length, at adiopter of 0 m⁻¹, of an entire system from the image plane to an exitsurface of the eyepiece system.
 34. A camera according to claim 30,further satisfying the following condition: 15 mm<Y′<30 mm
 35. A cameracomprising: a plurality of reflection surfaces for erecting an image onan image plane; and an eyepiece system with positive refracting powerfor observing the image, wherein the eyepiece system comprises, in orderfrom an object side, a first lens component with positive refractingpower, a second lens component with positive refracting power, and athird lens component with negative refracting power so that spacingsbetween the first lens component and the second lens component andbetween the second lens component and the third lens component arechanged to thereby make a diopter adjustment, and the camera satisfiesthe following conditions:0.15<tan(S)<0.352.70<f′b/Y′<3.20−0.80<f3/f″<−0.40 where S is an angle,at a diopter of 0 m⁻¹, made by a most off-axis chief ray passing througha point on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;f′b is an air-equivalent length, at a diopter of 0 m⁻¹, from the imageplane to an entrance surface of the first lens component; Y′ is adiagonal length of a picture plane on the image plane; f3 is a focallength of the third lens component; and f″ is a focal length, at adiopter of 0 m⁻¹, of an entire system from the image plane to an exitsurface of the eyepiece system.
 36. A camera comprising: a plurality ofreflection surfaces for erecting an image on an image plane; and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power, and a third lens componentwith negative refracting power so that spacings between the first lenscomponent and the second lens component and between the second lenscomponent and the third lens component are changed to thereby make adiopter adjustment, and the camera satisfies the following conditions:0.15<tan(S)<0.352.00<f′b/Y′<4.00−0.65<f3/f″<−0.45 where S is an angle,at a diopter of 0 m⁻¹, made by a most off-axis chief ray passing througha point on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;f′b is an air-equivalent length, at a diopter of 0 m⁻¹, from the imageplane to an entrance surface of the first lens component; Y′ is adiagonal length of a picture plane on the image plane; f3 is a focallength of the third lens component; and f″ is a focal length, at adiopter of 0 m⁻¹, of an entire system from the image plane to an exitsurface of the eyepiece system.
 37. A camera comprising: a plurality ofreflection surfaces for erecting an image on an image plane; and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power, and a third lens componentwith negative refracting power so that spacings between the first lenscomponent and the second lens component and between the second lenscomponent and the third lens component are changed to thereby make adiopter adjustment, and the camera satisfies the following conditions:0.15<tan(S)<0.352.00<f′b/Y′<4.00−0.65<f3/f″<−0.50 where S is an angle,at a diopter of 0 m⁻¹, made by a most off-axis chief ray passing througha point on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;f′b is an air-equivalent length, at a diopter of 0 m⁻¹, from the imageplane to an entrance surface of the first lens component; Y′ is adiagonal length of a picture plane on the image plane; f3 is a focallength of the third lens component; and f″ is a focal length, at adiopter of 0 m⁻¹, of an entire system from the image plane to an exitsurface of the eyepiece system.
 38. A camera comprising: a plurality ofreflection surfaces for erecting an image on an image plane; and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power, and a third lens componentwith negative refracting power so that spacings between the first lenscomponent and the second lens component and between the second lenscomponent and the third lens component are changed to thereby make adiopter adjustment, and the camera satisfies the following conditions:0.15<tan(S)<0.352.70<f′b/Y′<3.20−0.80<f3/f″<−0.40 where S is an angle,at a diopter of 0 m⁻¹, made by a most off-axis chief ray passing througha point on an optical axis at a distance of 23 mm along the optical axisfrom an exit surface of the third lens component with the optical axis;f′b is an air-equivalent length, at a diopter of 0 m⁻¹, from the imageplane to an entrance surface of the first lens component; Y′ is adiagonal length of a picture plane on the image plane; f3 is a focallength of the third lens component; and f″ is a focal length, at adiopter of 0 m⁻¹, of an entire system from the image plane to an exitsurface of the eyepiece system.
 39. A camera comprising: a plurality ofreflection surfaces for erecting an image on an image plane; and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power, and a third lens componentwith negative refracting power, and the camera satisfies the followingconditions: 2.5<f′b′/Y′<4.0−1.0<f3/f′″<−0.20.4<f1/f′″<0.95 where f′b′ isan air-equivalent length, at a diopter of −0.5 (m⁻¹), from the imageplane to an entrance surface of the first lens component; Y′ is adiagonal length of a picture plane on the image plane; f3 is a focallength of the third lens component; f1 is a focal length of the firstlens component; and f′″ is a focal length of an entire system from theimage plane to an exit surface of the eyepiece system at a diopter of−0.5 (m⁻¹).
 40. A camera comprising: a plurality of reflection surfacesfor erecting an image on an image plane; and an eyepiece system withpositive refracting power for observing the image, wherein the eyepiecesystem comprises, in order from an object side, a first lens componentwith positive refracting power, a second lens component with positiverefracting power consisting of a single meniscus lens element with aconvex surface directed toward the object side, and a third lenscomponent with negative refracting power as a whole in which apupil-side surface is stronger in refracting power than an object-sidesurface, and the camera satisfies the following conditions:2.5<f′b′/Y′<4.0−1.0<f3/f′″<−0.20.4<f1/f′″<0.95 where f′b′ is anair-equivalent length, at a diopter of −0.5 (m⁻¹), from the image planeto an entrance surface of the first lens component; Y′ is a diagonallength of a picture plane on the image plane; f3 is a focal length ofthe third lens component; f1 is a focal length of the first lenscomponent, and f′″ is a focal length of an entire system from the imageplane to an exit surface of the eyepiece system at a diopter of −0.5(m⁻¹).
 41. A camera comprising: a plurality of reflection surfaces forerecting an image on an image plane; and an eyepiece system withpositive refracting power for observing the image, wherein the eyepiecesystem comprises, in order from an object side, a first lens componentwith positive refracting power, a second lens component with positiverefracting power consisting of a single meniscus lens element with aconvex surface directed toward the object side, and a third lenscomponent with negative refracting power as a whole in which apupil-side surface is stronger in refracting power than an object-sidesurface, and the camera satisfies the following conditions:2.5<f′b′/Y′<4.00.4<f1/f′″<0.95 where f′b′ is an air-equivalent lengthfrom the image plane to an entrance surface of the first lens component;Y′ is a diagonal length of a picture plane on the image plane; f1 is afocal length of the first lens component, and f′″ is a focal length ofan entire system from the image plane to an exit surface of the eyepiecesystem at a diopter of −0.5 (m⁻¹).
 42. A camera comprising: a pluralityof reflection surfaces for erecting an image on an image plane; and aneyepiece system with positive refracting power for observing the image,wherein the eyepiece system comprises, in order from an object side, afirst lens component with positive refracting power, a second lenscomponent with positive refracting power consisting of a single meniscuslens element with a convex surface directed toward the object side, anda third lens component with negative refracting power as a whole inwhich a pupil-side surface is stronger in refracting power than anobject-side surface, and the camera satisfies the following conditions:−1.0<f3/f′″<−0.20.4<f1/f′″<0.95 where f3 is a focal length of the thirdlens component; f1 is a focal length of the first lens component, andf′″ is a focal length of an entire system from the image plane to anexit surface of the eyepiece system at a diopter of −0.5 (m⁻¹).
 43. Acamera comprising: a plurality of reflection surfaces for erecting animage on an image plane; and an eyepiece system with positive refractingpower for observing the image, wherein the eyepiece system comprises, inorder from an object side, a first lens component with positiverefracting power, a second lens component with positive refracting powerconsisting of a single meniscus lens element with a convex surfacedirected toward the object side, and a third lens component withnegative refracting power as a whole in which a pupil-side surface isstronger in refracting power than an object-side surface, and the camerasatisfies the following conditions: 0.4<f1/f′″<0.95 where f1 is a focallength of the first lens component and f′″ is a focal length of anentire system from the image plane to an exit surface of the eyepiecesystem at a diopter of −0.5 (m⁻¹).
 44. A camera according to claim 39 or40, further satisfying the following condition: 16.0<Y′<28.0